By way of annotating the sound/spelling changes: k and g sounds were interchangeable -- and indeed gu (ぐ) is written now as ku (く) with a breath mark that hadn't been invented yet -- and likewise for zu (ず) and s (す); vowels without an initial consonant were often (the rules for exactly when don't matter for these purposes) pronounced with an initial h or f, and so i was essentially interchangeable with hi for this game.

---L.